The structure of an IC card that is being mass-produced at present is disclosed in “IC card” (edited by Corporation of the Institute of Electronics, Information and Communication Engineering and published by Ohm Co., Ltd. on May 25, 1990, first edition, pp. 33). FIG. 13 illustrates a cross sectional structure of its representative main portion. As is illustrated in FIG. 13, the conventional IC card includes a module substrate 44 having a conductor circuit, an IC chip 43 implemented on the module substrate, pads 42 provided on the IC chip, and bonding wires 41 to which terminals of the module substrate are connected.
FIG. 4 is a plan view illustrating an IC chip in which wires are bonded. In this method using the wires, a semiconductor active area 102 on the IC chip and bonding pads 42 thereon are situated at different regions with each other. A bonding wire head 132 is a portion situated at the head of a bonding wire 41.
FIG. 5 illustrates a cross section of the bonding portion illustrated in FIG. 4. The bonding pad 42, which is formed on an IC chip 44, is pressed strongly by the bonding wire head 132 at the time of the bonding. The bonding wire 41 is pressed by a mechanical operation, thereby being caused to be connected to the bonding pad. This sometimes results in a destruction of an active element if it exists under the bonding pad. Accordingly, in the prior art, it was impossible to locate the active element.
Also, in the case of an IC chip of 0.3 mm square that is used in, for example, an IC tag, although size of the bonding pad is in the range of 0.1 to 0.15 mm square and the number of the bonding pads is in the range of about 2 to 10, it turns out that an area that the bonding pads occupy on the IC chip becomes considerably large.
Incidentally, the IC chip is about 200 to 400 μm thick. In this extent of thickness, especially when a main semiconductor material of which the IC chip is composed is a fragile silicon, there existed a fear that the IC chip is cracked if a bending stress is applied thereto. The larger the IC chip gets, the more apparent this tendency becomes. Conventionally, in order to prevent the IC chip from being cracked, it was necessary to select and use a bending-resistant material as a casing material so that no bending stress is applied to the IC chip. In order to solve this problem, an IC card using a flexible IC chip made thin up to about 1 μm is disclosed in JP-A-3-87299. Concerning the IC card disclosed here, however, it has been found that the following problem exists: Since the IC chip thus thinly filmed is located on the surface of the card substrate, the IC chip is torn if the bending stress especially an expansion stress is applied to the card.
As a method for solving problems like this, JP-A-7-99267 discloses a method of embodying a configuration that a thin type IC chip is provided substantially in proximity to the center of the IC card. In this technique, the pads on the IC chip and electrodes provided on the circuit substrate by printing are set so that they are exposed onto the same plane, and then interconnections between the pads on the IC chip and the electrodes on the circuit substrate are formed by printing with the use of a conductive paste, thereby connecting them electrically. The use of the conductive paste makes it unnecessary to execute the process of the wire bonding, which is economical in fabricating the IC card.
It has become obvious, however, that there exists the following problem when the connection with the pads on the IC chip is established by the above-described printing with the use of the conductive paste: That is to say, since a pitch of the pads formed on the existing IC chip is small and falls in the range of 100 to 150 μm, the wire bonding is capable of establishing the connection, whereas screen printing with the use of a silver paste is not capable of establishing the connection. Namely, this is a problem that, with the use of the existing technique, it is difficult to make the printing accuracy 200 μm or less. This problem becomes a serious trouble when the IC chip in which the conventional wire bonding is performed is used without any improvements or modifications.
It is an object of the present invention to provide a semiconductor device in which narrowly-pitched pads formed on an IC chip and electrodes provided on a substrate are connected electrically with each other by interconnections formed by printing, and a method of manufacturing the semiconductor device that allows them to be connected under a stable condition.
It is another object of the present invention to provide a highly reliable semiconductor device in which the narrowly-pitched pads formed on the IC chip and the electrodes printed on the substrate are connected electrically with each other, and a low cost method of manufacturing the semiconductor device that accompanies no increase in the number of the processing steps.